If all the world’s a stage, what the world really wants to do is direct.

Which is likely what inspired some 80,000 filmmakers to submit nearly 5,000 hours of homemade video footage to create the world’s very first YouTube documentary.

The one thing that united the final videos, chosen from 120 countries, was the date on which they were shot: exactly one year ago on July 24, 2010. The result is a 90-minute global portrait of life at its most beautiful and poignant. The film, produced by Ridley Scott and directed by Kevin Macdonald (“The Last King of Scotland”), opens in theaters today, including a gala premiere at MoMA.

One of the most striking contributions comes from a New Yorker living in Midtown East, 28-year-old David Jacques. In his apartment, he set up a tripod and camera, then recorded himself calling his 89-year-old grandmother to finally tell her that he was gay.

“I wanted it to come out one way,” says Jacques, who has since moved to Rhode Island. “And then as soon as I was on the phone, it came out in a way I didn’t anticipate. Afterward when I watched the clip, I thought, ‘Oh my God, they’re never going to use it.’ I was fighting tears back, and I felt like a mess. But that ended up being the reason they liked the clip, because it was real and very emotional and I guess people connected.”

Indeed, since the film’s screening at the Sundance Festival and January’s sneak peek on YouTube, Jacques has received hundreds of supportive e-mails.

“When I went to Sundance, I thought that my contribution was going to be 5 seconds, and then it came on, and it was the whole two and a half minute clip,” he says. “The other thing I didn’t realize is that my dog, Chipotle, is in the clip and she jumps off the couch when I come out. She’s like ‘Peace out!’ It was much needed comic relief for a pretty heavy clip.”

What kind of a dog?

“She’s a greyhound,” Jacques says. “A homophobic greyhound.”

New York contributor Caryn Waechter shot some of the most striking footage of a sunrise on the Staten Island Ferry and also caught children playing in fountains near the Intrepid. A professional filmmaker, Waechter describes the experience as a “spiritual” “magical” “love poem to her favorite city.” She shot all day long, getting up at 3 in the morning, and caught the sunrise for the first time in her life — and now it’s in a Ridley Scott movie.

“It was beautiful to look at

everyone facing this amazing city, some starting their day, and some ending their night,” she says. “It really makes you realize the vibrancy of how life is all around you.”

Other New York contributors included cinematographer Alan Teitel, 55, who caught gorgeous slow-motion footage of water being splashed on his 10-year-old daughter Clara’s head. He used his $30,000 camera (the kind normally reserved for industrial

analysis or military use to show bombs getting blown up) at a park in Port Washington, Long Island. When he saw the final film, Teitel said, “I was stunned at how they could weave all the individual sequences in with snips like mine.”

Alexander Rastopchin, 54, a musician who lives in Astoria captured his 12-year-old son Tal as he tickled him awake in the morning. “I want him to be more excited about life in general,” the father and filmmaker said. “He was very happy when he saw it. He felt like a movie star.”

Capturing Central Park, a couple dancing to an Italian song and even a sequence of tooth-brushing, Alberto Lama, a 37-year-old Upper East Side restaurant manager and photographer used a $250 camera and aimed to document the immigrant experience. “I wanted to show the life of a regular worker person,” says Lama, who is from Mexico City. “Maybe people can go back one day and see how people were living.”

Just like the videos posted on YouTube, every entry received its own brutally honest star rating, courtesy of “Life in a Day” editor Joe Walker.

“Ranking one star meant they’ve put less effort into filming it than we are putting into viewing it,” says Walker, who worked with 23 assistant editors to cull prime clips from the pile. “Five stars is ‘This should be in the film or else fire me.’ Then after a while we developed a six rating, which is: ‘It’s so bad it’s good.’ ”

Editor Walker says all the contributors influenced the aesthetic of the film, but he points to Jacques’ clip, which the editors saw at the beginning of the sorting process.

“That’s the benchmark,” he said. “Early on it was a useful way of saying, look at this five-star clip. I do most of my work in drama and feature films, and if you could get an actor to be that real, you know? You could never script it quite that way. You could never achieve quite that level of reality.”